The invention relates to a method of solar cell external interconnection and a solar cell panel made by the method.
There is a need for an improved method to electrically interconnect ultra-thin glass solar cell arrays to a carrier panel for a spacecraft, for example, with little or no damage to the solar cells or the interconnections thereof with the carrier. Present methods of ultra-thin glass solar cell array attachment and interconnection, including thermal compression and ultrasonic bonding, can damage the solar cell PN junction and also the glass because the high temperature and/or pressure bonding probe directly contacts the solar cell PN junction during the solar interconnection process.
Another problem with present methods is that the RTV silicone adhesive used to attach the solar cells to the carrier takes hours to cure. This curing time prevents fast automated solar cell connection to the carrier. The adhesive also does not permit tight tolerance manufacturing processes. Even if the solar cell is held in place during the conventional bonding process to speed up the attachment of the solar cells to the carrier, the high temperature probe in thermal compression bonding damages the RTV silicone adhesive attachment because the adhesive cannot withstand the temperature of the bonding probe.
The improved method of solar cell external interconnection and the solar cell panel made thereby according to the present invention avoid the aforementioned problems. The bonding force in the disclosed embodiment of the method is reduced in comparison with the conventional methods while the heat for bonding is localized at the bond area(s) and is applied for only a very short time. More specifically, a method of a solar cell external interconnection according to the invention comprises providing an assembly including a solar cell module, a flexible lead frame to which the solar cell module is to be interconnected and a solder located between the solar cell module and the flexible lead frame.
The solder is heated by directing a hot gas into the area of the solder to melt the solder and form a soldered connection between the solar cell module and the lead frame.
In the disclosed embodiments, the solder is provided at a plurality of discrete sites between the solar cell module and the flexible lead frame and a plurality of soldered connections are formed at the same time during the heating.
The soldered assembly is then attached to a module carrier panel by applying a first, flexible adhesive and a second, thermally curable adhesive to respective areas of the module carrier panel. The soldered assembly is placed on the adhesives on the module carrier panel to embed a portion of the assembly in the flexible adhesive and another portion of the assembly in the thermally curable adhesive. The assembly and module carrier panel are heated to cure the thermally curable adhesive to anchor the assembly on the modular carrier panel.
A solar cell panel according to the invention comprises an assembly of at least one solar cell module and a flexible lead frame connected to the solar cell module by at least one soldered connection. A module carrier panel is attached to the assembly in respective areas by a first, flexible adhesive in which a portion of the assembly is embedded and a second, thermally cured adhesive anchoring the assembly on the module carrier. In one form of the invention, a plurality of the assemblies are attached to the module carrier panel with the lead frames of at least two adjacent assemblies being connected to one another by a pin connection. In another form of the invention, a plurality of solar cell modules are each connected with the flexible lead frame by at least one soldered connection and, in turn, attached to the module carrier panel without pin connection. The solar cell modules can be connected in series or parallel in the solar cell panels, with or without pin connection.
These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of several embodiments of the invention taken with the accompanying drawings.